Electrode-carrying catheter and method of making same

ABSTRACT

An electrode-carrying catheter has elongate, flexible tubing defining a proximal end, a distal end, and an electrically insulative outer tubular layer intermediate the ends, the tubing including a flexible electrically conductive core of wire and a flexible non-conductive core-covering layer of plastic about the core. At least one electrically conductive ring electrode is crimped on and flush with the outer tubular surface. In order to conduct electrical signals between the proximal end and each of the ring electrodes, a longitudinally-spaced plurality of flexible electrically conductive wires are helically wound around and at least partially into the core-covering layer. The wound wires define a removed section beneath a segment of each of the ring electrodes to enable electrical contact between a respective one of the wound wires and a respective one of the ring electrodes An electrically conductive flexible flat ribbon is disposed intermediate each of the ring electrodes and the tubing, each ribbon being electrically and physically joined to a respective one of the wound wires and wrapped about the outer tubular surface, each of the ring electrodes being crimped onto a respective one of the ribbons and the outer tubular surface.

BACKGROUND OF THE INVENTION

The present invention relates to electrode-carrying catheters, and moreparticularly to an inexpensive and reliable electrode-carrying catheterand a method of making the same.

Electrode-carrying catheters as well know in the medical art and finddiagnostic and therapeutic utility in a wide variety of differentapplications. For example, mapping catheters are used diagnostically toproduce a wave function of the heart's electrical impulses so that adoctor can determine proper functioning or fault, and location of thefault, in the heart Ablative catheters are used therapeutically todestroy tissue in the heart causing tachycardia, utilizing radiofrequency current catheter ablation. Such catheters are also used forheart pacing purposes and for analgesia in various parts of the body.Depending upon the particular application for which the catheter isused, it may be desirable for the catheter to carry one or more sideelectrodes, one or more end electrodes, or a combination thereof. Theuse of a plurality of smaller electrodes rather than a single largeelectrode enables higher current densities to be obtained and frequentlyenables superior electrical contact with the tissue, both of these beinghighly desirable factors in connection with ablative catheters inparticular, where larger areas of radio frequency ablation in the tissueare desirable.

Electrically conductive wires have never proven to be entirelysatisfactory as the electrodes since a functional electrode requires amuch larger surface area than can be provided by a flexible wire.Further, unless provisions are made to fix the wire relative to thecatheter tubing, it is extremely difficult to ensure that the wire isheld in place so as to assure a reliable electrical contact. While awire could be held in place by use of an electrically conductiveadhesive securing the wire to the tubing, it would be extremelydifficult to create an electrode by applying an adhesive in a thin layerover a large surface area, as would be necessary to ensure that theelectrode layer is flexible.

While a biocompatible conductive paint as an electrode has the advantageof being easily applied in an extremely thin layer to the tubing outersurface by printing techniques, so as to ensure flexibility thereof andcover the wire, there are other problems associated with such conductivepaint. While the flexible, thin layer of conductive ink painted on thetubing outer surface forms a good electrical connection with the wire,the conductive paint does not form a reliable physical connection withthe typical wire, as necessary to ensure that the passage of thecatheter through the human body along the guidewire to the proposedworking site does not to some degree remove, separate or abrade away thethin layer of conductive paint.

Typically electrode-carrying catheters are made by applying metal stripson the outer side and/or distal (front) surfaces of a flexible tubing ofnon-conductive plastic, each side strip acting as a side or ringelectrode and each distal strip acting as an end electrode. The presenceof the metal strips limits the natural flexibility of the tubing so thatthe catheter is not of high flexibility throughout its entire length andthis presents problems in threading the catheter into the human bodyover a guidewire since the diminished flexibility may limit the abilityof the catheter to conform to the travel path defined by the guidewire,leading to blood vessel trauma. Nonetheless, such catheters carryingring electrodes are in favor because of the high level of reliability ofthe electrical connections therein.

The conventional processes for forming ring or metal band electrodesflush with the outer surface of a catheter are arduous, time-consumingand/or require further processing. For example, in one process metalbands and sleeves therebetween are slipped over the tubing outer surfacewith the sleeves maintaining the appropriate spacing between adjacentelectrodes; this requires the use of additional pieces (namely, thesleeves) and an arduous assembly process. Another process requires thetubing to be stretched to lower the outer diameter thereof, metal bandsplaced over the stretched tubing and disposed in appropriate spatialrelationship, and the tubing then heated and released. The metal bandssink into the heat-softened tubing outer surface as the tubing resumesits original configuration (except where the metal bands are embeddedtherein). This technique requires additional stretching, heating andcooling steps.

Accordingly, it is an object of the present invention to provide in oneembodiment an electrode-carrying catheter having a ring or metal bandelectrode thereon flush with the catheter outer surface.

Another object is to provide such a catheter which can mount a largenumber of electrodes.

A further object is to provide such a catheter wherein there is areliable adhesive-free electrical contact between an electrode and anyconductive wire extending from the proximal end to the electrode, theelectrode has a sufficiently large surface area for electrodefunctioning, and all exposed surfaces are biocompatible.

It is also an object of the present invention to provide such a catheterwhich is easily and inexpensively manufactured.

It is another object to provide processes for the manufacture of suchcatheters.

SUMMARY OF THE INVENTION

It has now been found that the above and related objects of the presentinvention are obtained in an electrode-carrying catheter of low cost andhigh reliability, comprising elongate flexible tubing defining aproximal end, a distal end, and an electrically insulative outer tubularlayer intermediate the ends. The tubing includes a flexible electricallyconductive core of wire and a flexible non-conductive core-coveringlayer of plastic about the core. At least one electrically conductivering electrode is crimped on and flush with the outer tubular surface.Conducting means are provided for conducting electrical signals betweenthe proximal end and each of the ring electrodes. The conducting meansincludes, intermediate the core and the outer tubular layer, alongitudinally-spaced plurality of flexible electrically conductivewires helically wound around and at least partially into thecore-covering layer and insulated from one another at least by thecore-covering layer and from the environment at least by the outertubular layer. The outer tubular layer and any electrical insulationabout the wound wires define a removed section beneath a segment of eachof the ring electrodes to enable electrical contact between a respectiveone of the wound wires and a respective one of the ring electrodes. Theconducting means further includes electrically conductive flexible flatmeans disposed intermediate each of the ring electrodes and the tubing,each of the flat means being electrically and physically joined to arespective one of the wound wires and wrapped about the outer tubularlayer. Each of the ring electrodes is crimped onto a respective one ofthe flat means and the outer tubular layer.

Preferably, the core is a stranded configuration of annealed stainlesssteel wire having an appreciable torsional strength and a slow returnafter lateral bending. The core-covering layer and the outer tubularlayer are formed of polyurethane. The core-covering layer is softer thanthe outer tubular layer. The core-covering layer is over-extruded overthe core, and the outer tubular layer is over-extruded over the woundwires and the core-covering layer. Where each of the wound wires iscovered with electrical insulation, the electrical insulation coveringeach wound wire defines a removed section beneath one of the electrodes.

Preferably, the flat means is a flat copper ribbon having a pair ofopposed ends, the ribbon being electrically and physically joined at oneend to a respective one of the wound wires wrapped under tensioncompletely about the outer tubular layer, and physically joined at theother end to itself. The flat means is preferably joined to the woundwires by welding.

Preferably, the electrodes are platinum with a minor proportion ofiridium. Each of the ring electrodes is crimped onto the flat means andthe outer tubular layer at at least 24 crimp points. In a preferredembodiment, the ring electrodes crimped onto the flat means and theouter tubular layer are also welded to the flat means, and the outertubular layer is reformed about the ring electrodes.

Where the core has an extension projecting distally from the distal end,an electrically conductive end electrode is crimped distally onto thecore extension and is proximally crimped onto and radially flush withthe outer tubular layer.

The present invention also encompasses a process for manufacturing anelectrode-carrying catheter of high reliability, comprising the step ofover-extruding a soft outer layer of plastic over a flexible,electrically conductive, elongate core of wire. A spaced apart pluralityof flexible, electrically conductive wires is helically wound about andat least partially into the soft outer layer. A flexible, non-conductinghard outer layer of plastic is over-extruded over the wound wires andthe soft outer layer. Portions of the hard outer layer, and anyinsulation about the wound wires, are removed at a plurality of edlocations so as to expose a portion of each of the wound wires. Theremoved portions at each location are replaced with an electricallyconductive flexible ribbon electrically and physically joined to arespective one of the wound wires and wound about the wound wires andhard outer layer. An electrically conductive ring electrode is crimpedonto each of the ribbons and the bard outer layer thereabout at eachspaced location, flush with the hard outer layer, the ribbons conductingelectrical signals between a respective one of the exposed wire portionsand a respective one of the ring electrodes.

BRIEF DESCRIPTION OF THE DRAWING

The above and related objects, features, and advantages of the presentinvention will be more fully understood by reference to the followingdetailed description of the presently preferred, albeit illustrative,embodiments of the present invention when taken in conjunction with theaccompanying drawing wherein:

FIG. 1 is a fragmentary side elevational view of an electrode-bearingcatheter according to a preferred embodiment of the present invention,with three side electrodes and one end electrode;

FIG. 2 is a fragmentary side elevational view of the tubing and woundwires thereof, to a slightly enlarged scale;

FIG. 3 is a fragmentary sectional view taken along the line 3--3 of FIG.2, to a greatly enlarged scale;

FIGS. 4A-4D are schematics illustrating the process of applying the flatribbon to the tubing;

FIG. 5 is a fragmentary longitudinal sectional view of the catheterafter crimping of the ring electrodes thereon;

FIG. 6 is a transverse sectional view thereof to an enlarged scale, withthe crimps being greatly exaggerated for expository purposes;

FIG. 7 is a transverse fragmentary sectional view thereof taken alongthe line 7--7 of FIG. 5, to a greatly enlarged scale, with the crimpsbeing greatly exaggerated for expository purposes;

FIG. 8 is a fragmentary exploded side elevational view of the catheterand end electrode assembly; and

FIG. 9 is a side elevational view of the assembly of FIG. 8 aftercrimping, with the crimps being greatly exaggerated for expositorypurposes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, therein illustrated is an electrode-carryingcatheter according to the present invention, generally designated by thereference numeral 10. While the configuration and dimensions of thecatheter will vary with the intended application for the catheter, it isgenerally of the same overall width and length of the known cathetersfor the same application. The catheter 10 is formed of elongate,flexible tubing generally designated 12. The tubing 12 defines aproximal end 14, a distal end 16, and a sidewall or outer tubular layer20 connecting the ends 14, 16 and having an electrically insulativeouter surface 21.

Referring now to FIGS. 2-4 as well, at least one electrode 30 isdisposed on the tubing 12. The electrode may be a side electrode 30adisposed on the outer surface 21 (three side electrodes beingillustrated in FIG. 1), an end electrode 30b disposed on the distal orfront end 16 (one end electrode being illustrated in FIG. 1), or acombination thereof. Particular ring electrodes 30a may extendpredominantly axially or transversely (i.e., circumferentially) relativeto the tubing axis as preferred for a given application. Preferably theside electrode 30a extends fully around the circumference of the tubing12, and the end electrode 30b extends over the full diameter of thedistal end 16 (as illustrated). Conducting means, generally designated29, are provided for conducting electrical signals between the proximalend 14 and each of the electrodes 30a, 30b, 30a, 30b.

Referring now to FIGS. 2 and 3, the tubing 12 is composed initially of aflexible, conductive core 42 and a flexible, insulating, soft,core-covering layer 44 disposed over the outer surface of the core 42.The soft or core-covering layer 44 may be formed by over-extruding (orotherwise forming) a soft plastic over the wire core 42, the soft layerbeing relatively softer than the wire core. The core 42 is preferablyformed of a wire exhibiting an appreciable degree of torsional stiffness(so that rotation of the proximal end 14 of the tubing is transmitted tothe distal end 16) and a slow return or recovery after a lateral bending(so that the catheter makes good contact along its length with the wallsof the vessel into which it is inserted). A preferred core 42 is a 0.032inch outer diameter length of a stranded and twisted configuration ofannealed wire, such as 304 stainless steel 7×19. (The annealing processinvolves heating the stainless steel wire--e.g., to 2,000° F.--so thatit becomes formable and tends to retain a configuration into which it isflexed without immediately springing back.) A preferred softcore-covering layer 44 is formed of a soft plastic such as polyurethanehaving a durometer hardness of 80A available under the trade nameTecoflex (from Thermedics Inc. of Woburn, Mass.).

As part of the conducting means, flexible, insulated, electricallyconductive wires 45 (three wires 45a, 45b, 45c being shown, one for eachside electrode 30a) are helically or spirally wound around and at leastpartially into the soft core-covering layer 44 about the core 42. Thewound wires 45 are longitudinally spaced apart such that each of thewires 45 is insulated from the two adjacent wires 45 by portions of thesoft layer 44 as well as the wire insulation. In order to precludeaccidental movement of the spaced apart plurality of wound wires 45prior to over-extrusion of a hard layer 20 thereover, the wires 45 arehelically or spirally wound around the soft layer 44 (under roughly handtension) so that they at least partially embed themselves within thesoft layer 44 (preferably at least 75% of the diameter becomingembedded). The wound wires 45 are preferably insulated magnet wireshaving a gauge of 34. As the soft layer 44 ensures electrical separationbetween the various wires 45, the wires are not insulated in order toprevent shorting if they come into contact, but merely to facilitatesubsequent processing steps. Indeed, uninsulated wires may used ifdesired. It will be appreciated that, while only three wires 45 havebeen illustrated, the number of wires 45 can be varied as desired forparticular applications depending on the number of side electrodes 30a.Each wire may be of a different color.

Finally, a flexible, thin insulating layer of plastic is over-extruded(or otherwise formed) over the soft core covering layer 44 and anyexposed portion of wound wires 45 to form the hard outer layer 20 of thetubing 12 defining outer surface 21. The hard layer 20 may be formed ofpolyurethane or any of the other flexible, but hard, electricallyinsulative plastics commonly used in catheter construction such aspolyvinyl chlorides, polyesters and various copolymers. The hard layer20 is preferably formed of polyurethane having a durometer hardness of71D available under the trade name Tecothane (from Thermedics Inc.).Thus the conductive wires 45 are isolated from one other and theenvironment by means of the core 42, the soft layer 44, and the hardlayer 20 as well as any insulation thereon.

The hard layer 20 is preferably over-extruded to a thickness slightlygreater than that ultimately desired so that it may be subsequentlyground down (preferably using a conventional centerless grindingmachine) down to a constant outer diameter, thereby maskingirregularities originally present due to the presence of the wires 45wound on the soft layer 44.

If the soft core-covering layer 44 is of sufficient thickness to receiveand electrically isolate the wound wires 45 (which must then be totallyembedded therein) and is furthermore subsequently treatable (e.g.,curable or modifiable) to provide an abrasion-resistant surface,application of the hard layer 20 may be dispensed with entirely and thesoft layer 44, thus treated after the wires 45 are totally embeddedtherein, will also serve as the hard layer 20.

Referring now to FIG. 4A, next, the hard layer 20 of the tubing 12 isremoved at a plurality of spaced locations along its circumferentialsidewall 21 (corresponding to the ultimate locations of the sideelectrodes 30a) so as to form windows 47. Each window 47 exposes aportion of a respective one of the wound wires 45 at its respectivelocation. The hard layer 20 can be removed at the desired locations byvarious techniques such as cutting, skiving, drilling or grinding, butgrinding or cutting is preferred as they are easy, quick and preciseoperations. The windows are preferably formed using a grinding wheelhaving a diameter suitable for forming windows of the desired size (suchas a 0.020 inch diameter) until the grinding has removed a suitableamount of the hard layer 20 and, where present, the insulation about thewire 45, so as to expose the conductive element of the wire 45.

Referring now to FIG. 8, in a similar fashion the hard layer 20 at thedistal end 16 of the tubing 12 is removed (e.g., ground by a grindingwheel) in order to remove from the distal end 16 the hard outer layer 20and, where present, the insulation about the end of the core 42.Grinding of the distal end 16 continues until there is exposed anappropriate length (about 0.035 inch) of the conductive element of thecore wire 42, this exposed conductive element projecting forwardly fromthe distal end 16 of the tubing 12 as a core extension 42a

It will also be appreciated that the hard layer 20 of the sidewall 21may have the portions at the particular locations removed therefromsimultaneously to form windows 47. The locations at which the hard layer20 is to be removed are predetermined by the desired location of theelectrodes 30a. Before removal of the portions of the hard layer 20, thewound wires 45 are already in place and in fixed spatial dispositionrelative to one another. Accordingly, once the location of one wire 45is determined (perhaps by inspection of the distal end 16 where they areinitially visible), then the location of all of the remaining wires 45is known. Thus, grinding elements of a grinding machine, for example,can be appropriately positioned relative to the known wire, and thedesired portions of the bard layer 20 (and, when present, the wireinsulation) simultaneously removed at each location. This enables thewindows 47 to be inexpensively formed in a low labor operation.

Referring again to FIG. 4B, after creation of the windows 47, a flatconductive element 51, such as a flat copper ribbon (0.001×0.012 inch),is electrically and physically joined to the exposed portion of the wire45 under the window 47. Preferably the ribbon 51 is welded to theexposed wire 45 at point 48 using a welder such as that available underthe trade name Light Force Welder (from Unitek Equipment Inc. ofMonrovia, Calif.). Typically, a free ribbon end 51a is first welded tothe wire 45. Referring now to FIG. 4C, the ribbon 51 and the tubing 10are then rotated relative to one another until a shank 51b of the ribbon51 is wrapped completely one turn (360°) about the hard layer 20, andback on itself. This may be accomplished by rotating the tubing 12 whileusing a machine to maintain hand tension on the ribbon 51. Next, the asyet unwelded ribbon end 51c of the loop thus formed is welded to theribbon 51 at point 49 (preferably at the already welded ribbon end 51a).Finally, as seen in FIG. 4D, the ribbon 51 is removed from the ribbonspool (not shown), e.g., by simply applying a quick tug to the ribbon.

While there is an overlap of the ribbon 51c upon itself 51a, the extrathickness of the additional ribbon layer is of no consequence since theribbon is so thin relative to the depth of the window 47. It will beappreciated that the ribbon performs the role of bringing the signalfrom the exposed wire (which is located below the hard layer 20) up tothe top of the hard layer 20 where it can be fed to an electrode 30a.Preferably the welding equipment uses the electrodes available under thetrade name Unitip 111L (available from Unitek Equipment Inc.) or asimilar microelectrode which permits the welding equipment toresistively weld the exposed wire 45 and the ribbon 51 together withinthe confines of window 47.

The application of the ribbon 51 to a wire 45 is then repeated for eachof the remaining windows 47, and the tubing 12 is then ready forapplication of the ring or metal electrodes 30.

Referring now to FIGS. 5-7, to form the side electrodes 30a, a metalband or ring electrode 53, preferably formed of a biocompatible metalsuch as platinum or an alloy of platinum hardened with 10% iridium, isslid along the length of the hard layer 20 of tubing 12 to anappropriate location to cover one of the windows 47. The inner diameterof the ring electrode 53 is slightly larger than the outer diameter ofthe tubing 12 to enable the electrode 53 to slide over the hard layer 20and over the top of the ribbon 51 at the location. The length of eachring electrode 53 (0.078 inch) is greater than the length of the window47 it covers, so that the ring electrode 53 also extends over theadjacent surfaces of the hard layer 20. A crimping machine (not shown)is then employed to crimp the outer diameter of the ring electrode 53down to the outer diameter of the tubing 12 (i.e., the hard layer 20).To this end, the crimping machine is provided with a circumferentiallyspaced plurality of crimping points (for example, 12 pointsequidistantly spaced about a circumference) which simultaneously crimpand collapse the band of electrode 53 to a preset diameter (e.g., 0.078inch) so that the crimped or collapsed band retains its originalcircular configuration but with a reduced diameter. Preferably thecrimping machine and the catheter workpiece are then relatively rotated(e.g., 15°) and crimping is performed a second time (thus making, forexample, 24 equidistantly spaced crimp points), thereby to flatten outany high spots left by the first crimping. The length of each crimp isgreater than the ribbon 51 so that each ring electrode 53 is crimpedonto both ribbon 51 and the adjacent surfaces of the hard layer 20. Theribbon ends 51a, 51c and the ring electrode 53 are typically spacedapart, electrical contact between ribbon 51 and ring electrode 53 beingeffected through ribbon shank 51b.

It will be appreciated that, because the crimping operation squeezes theelectrode band 53 flush with the tubing outer surface 21, an extremelysmooth tubing/electrode interface is obtained without increasing thediameter of the tubing 12. Typically no subsequent hand smoothing of theexterior surface of the tubing at the tubing/electrode interface isrequired.

Accordingly, the present invention employs a crimping process whichoffers a significant cost advantage over conventional processes forproducing a catheter with a flush outer surface by sharply reducinglabor requirements and simplifying assembly. While crimping of the sideelectrodes 53 on the tubing 12 suffices to electrically and physicallysecure the electrode 53 to the ribbon 51 and hence to the associatedexposed wound wire 45, excessive bending of the catheter during use maystill result in a separation of elements enabling the electrode 53 tomove relative to the ribbon 51 and hard layer 20. Accordingly, for extrasecurity the ring electrode 53 is preferably finally welded to theribbon 51. The welding may be performed using a conventional resistivewelder with two electrodes which have been machined to the diameter ofthe electrode 53 so that the welder cannot damage the electrode underthe pressure of the weld. A preferred resistive welder is availableunder the trade name Thin Line Welder (from Unitek Equipment Inc.).

As a highly-desirable by-product of the welding process, the heatgenerated thereby melts the hard layer 20 underneath the electrode 53,allowing it to reform and securely attach itself to the electrode 53.Accordingly, the electrode 53 adheres better to the hard layer 20 aswell as the ribbon 51 and is less likely to separate therefrom duringsubsequent flexure of the catheter, thus enhancing reliability of theproduct.

The manufacturing process of the present invention is in all its aspectseasy and inexpensive relative to the labor-intensive nature of mostother manufacturing processes for producing an electrode carryingcatheter, while affording a product of enhanced reliability.

Referring now to FIG. 8, where the catheter 10 includes at least one endelectrode 30b as one of the electrodes 30 thereof, the electricallyconductive end electrode is preferably configured and dimensioned as aflexible cap, generally designated 60, disposed across the distal end 16of the tubing 12 in order to close the same. The cap 60 may be formed ofthe same material as the ring electrodes or a different material. Thecap 60 is of appreciable thickness and has a head 64 defining a recess62 on its proximal surface and a proximally projecting circumferentialband 66. As cap 60 is slipped over the distal end, the core extension42a is received within cap recess 62, and the distal end of the hardlayer 20 is received within the cap band 66. Referring now to FIG. 9,the head or cap distal end 64 is then crimped onto the core extension42a, at 80, and the band or cap proximal end 66 is crimped onto andflush with the hard layer 20, at 82. This double crimping 80, 82, usinga crimping machine as described hereinabove in connection with thecrimping of the side electrodes 30a, securely joins the end electrode30b with the core extension 42a and hard layer 20, neither a ribbon 51nor a welding step being required.

As used herein, the terms "insulating", "insulative", "non-conducting"and "non-conductive" are synonyms.

To summarize, the present invention provides an electrode-carryingcatheter of high reliability and low cost, the catheter being capable ofmounting a large number of electrodes. There is reliable adhesive-freeelectrical contact between an electrode and any conductive wireextending from the proximal end to the electrode, with the electrodehaving a sufficiently large surface area for electrode functioning, andall exposed surfaces being biocompatible. The catheter is easily andinexpensively manufactured.

Now that the preferred embodiments of the present invention have beenshown and described in detail, various modifications and improvementsthereon will become readily apparent to those skilled in theAccordingly, the spirit and scope of the present invention is to beconstrued broadly and limited only by the appended claims, and not bythe foregoing specification.

I claim:
 1. An electrode-carrying catheter, comprising:(A) elongate,flexible tubing defining a proximal end, a distal end, and anelectrically insulative outer tubular layer intermediate said ends, saidtubing including a flexible electrically conductive core of wire and aflexible non-conductive core-covering layer of plastic about said core;(B) at least one electrically conductive ring electrode crimped on andflush with said outer tubular layer, and (C) conducting means forconducting electrical signals between said proximal end and each of saidat least one ring electrode, said conducting means including,intermediate said core and said outer tubular layer, alongitudinally-spaced plurality of flexible electrically conductivewires helically wound around and at least partially into saidcore-covering layer and insulated from one another at least by saidcore-covering layer and from the environment at least by said outertubular layer, said outer tubular layer defining a removed sectionbeneath a segment of each of said at least one ring electrode to enableelectrical contact between a respective one of said wound wires and arespective one of said at least one ring electrode, said conductingmeans further including electrically conductive flexible flat meansdisposed intermediate each of said at least one ring electrode and saidtubing for providing electrical communication between one of said atleast one ring electrode and one of said wound wires, each of said flatmeans being electrically and physically joined to a respective one ofsaid wound wires and wrapped about said outer tubular layer, each of atleast one ring electrode being crimped onto a respective one of saidflat means and said outer tubular layer.
 2. The catheter of claim 1wherein said flat means is joined to said wound wires by welding.
 3. Thecatheter of claim 1, wherein said core-covering layer is softer thansaid outer tubular layer.
 4. The catheter of claim 1, wherein saidcore-covering layer is over-extruded over said core, and said outertubular layer is over-extruded over said wound wires and saidcore-covering layer.
 5. The catheter of claim 1, wherein said flat meansis a flat copper ribbon having a pair of opposed ends, said ribbon beingelectrically and physically joined at one end to a respective one ofsaid wound wires, wrapped under tension completely about said outertubular layer, and physically joined at the other end to itself.
 6. Thecatheter of claim 1, wherein said core is a stranded and twistedconfiguration of annealed stainless steel wire having an appreciabletorsional strength and a slow return after lateral bending.
 7. Thecatheter of claim 1 wherein said core-covering layer and said outertubular layer are formed of polyurethane.
 8. The catheter of claim 1wherein each of said wound wires is covered with electrical insulation,and said electrical insulation covering each wound wire defines aremoved section beneath one of said at least one electrode.
 9. Thecatheter of claim 1 wherein said at least one electrode are platinumwith a minor proportion of iridium.
 10. The catheter of claim 1 whereineach of said at least one ring electrode is crimped onto said flat meansand said outer tubular layer at at least 24 crimp points.
 11. Thecatheter of claim 1 wherein said at least one ring electrode crimpedonto said flat means and said outer tubular layer are also welded tosaid flat means, and said outer tubular layer is reformed about said atleast one ring electrode.
 12. The catheter of claim 1 wherein said corehas an extension projecting distally from said distal end, and anelectrically conductive end electrode is crimped distally onto said coreextension and is proximally crimped onto and radially flush with saidouter tubular layer.
 13. The catheter of claim 1 wherein, said woundwires include electrical insulation thereabout, and said outer tubularlayer and said electrical insulation about said wound wires define saidremoval section.
 14. An electrode-carrying catheter, comprising:(A)elongate, flexible tubing defining a proximal end, a distal end, and anelectrically insulative outer tubular layer intermediate said ends, saidtubing including a flexible electrically conductive core of wire and aflexible non-conductive core-covering layer of plastic about said core,said core being a stranded and twisted configuration of annealedstainless steel wire having an appreciable torsional strength and a slowreturn after lateral bending, said core-covering layer being softer thansaid outer tubular layer and over-extruded over said core; (B) at leastone electrically conductive ring electrode crimped on and flush withsaid outer tubular layer; and (C) conducting means for conductingelectrical signals between said proximal end and each of said at leastone ring electrode, said conducting means including, intermediate saidcore and said outer tubular layer, a longitudinally-spaced plurality offlexible electrically conductive wires helically wound around and atleast partially into said core-covering layer and insulated from oneanother at least by said core-covering layer and insulated from oneanother at least by said core-covering layer and from the environment atleast by said outer tubular layer, said outer tubular layer defining aremoved section beneath a segment of each of said at least one ringelectrode to enable electrical contact between a respective one of saidwound wires and a respective one of said at least one ring electrode,said conducting means further including electrically conductive flexibleflat means disposed intermediate each of said at least one ringelectrode and said tubing for providing electrical communication betweenone of said at least one ring electrode and one of said wound wires,each of said flat means being a flat copper ribbon having a pair ofopposed ends, said ribbon being electrically physically joined bywelding at one end to a respective one of said wound wires, wrappedunder tension completely about said outer tubular layer, and physicallyjoined by welding at the other end to itself, each of said at least onering electrode being crimped onto a respective one of said flat meansand said outer tubular layer, said at least one ring electrode crimpedonto sad flat means and said outer tubular layer being also welded tosaid flat means, and said outer tubular layer being reformed about saidat least one ring electrode, said outer tubular layer beingover-extruded over said wound wires and said core-covering layer, saidcore having an extension projecting distally from said distal, end andan electrically conductive and electrode being crimped distally ontosaid core extension and proximally crimped onto and radially flush withsaid outer tubular layer.
 15. The catheter of claim 14 wherein, saidwound wires include electrical insulation thereabout, and said outertubular layer and said electrical insulation about said wound wiresdefine said removed section. .Iadd.
 16. An electrode-carrying catheter,comprising:(A) elongate, flexible tubing defining a proximal end, adistal end, and an electrically insulative outer tubular layerintermediate said ends, said tubing including a flexible electricallyconductive core of wire and a flexible non-conductive core-coveringlayer about said core; (B) at least one electrically conductive ringelectrode crimped on and flush with said outer tubular layer; and (C)conducting means for conducting electrical signals between said proximalend and each of said at least one ring electrode, said conducting meansincluding, intermediate said core and said outer tubular layer, alongitudinally-spaced plurality of flexible electrically conductivewires helically wound around and at least partially into saidcore-covering layer and insulated from one another at least by saidcore-covering layer and from the environment at least by said outertubular layer, said outer tubular layer defining a removed sectionbeneath a segment of each of said at least one ring electrode to enableelectrical contact between a respective one of said wound wires and arespective one of said at least one ring electrode, said conducting meanfurther including electrically conductive flexible flat means disposedintermediate each of said at least one ring electrode and said tubingfor providing electrical communication between one of said at least onering electrode and one of said wound wires, each of said flat meansbeing electrically and physically joined to a respective one of saidwound wires, and wrapped about said outer tubular layer, each of atleast one ring electrode being crimped onto a respective one of saidflat means and said outer tubular layer. .Iaddend..Iadd.17. The catheterof claim 16 wherein said flat means is joined to said wound wires bywelding. .Iaddend..Iadd.18. The catheter of claim 16 wherein saidcore-covering layer is softer than said outer tubular layer..Iaddend..Iadd.19. The catheter of claim 16 wherein said core-coveringlayer is over-extruded over said core, and said outer tubular layer isover-extruded over said wound wires and said core-covering layer..Iaddend..Iadd.20. The catheter of claim 16 wherein said flat means is aflat copper ribbon having a pair of opposed ends, said ribbon beingelectrically and physically joined at one end to a respective one ofsaid wound wires, wrapped under tension completely about said outertubular layer, and physically joined at the other end to itself..Iaddend..Iadd.21. The catheter of claim 16 wherein said core is astranded and twisted configuration of annealed stainless steel wirehaving an appreciable torsional strength and a slow return after lateralbending. .Iaddend..Iadd.22. The catheter of claim 16 wherein saidcore-covering layer and said outer tubular layer are formed ofpolyurethane. .Iaddend..Iadd.23. The catheter of claim 16 wherein eachof said wound wires is covered with electrical insulation, and saidelectrical insulation covering each wound wire defines a removed sectionbeneath one of said at least one electrode. .Iaddend..Iadd.24. Thecatheter of claim 16 wherein said at least one electrode is platinumwith a minor proportion of iridium. .Iaddend..Iadd.25. The catheter ofclaim 16 wherein each said at least one ring electrode is crimped ontosaid flat means and said outer tubular layer at at least 24 crimppoints. .Iaddend..Iadd.26. The catheter of claim 16 wherein said atleast one ring electrode crimped onto said flat means and said outertubular layer are also welded to said flat means, and said outer tubularlayer is reformed about said at least one ring electrode..Iaddend..Iadd.27. The catheter of claim 16 wherein said core has anextension projecting distally from said distal end, and an electricallyconductive end electrode is crimped distally onto said core extensionand is crimped proximally onto and radially flush with said outertubular layer. .Iaddend..Iadd.28. The catheter of claim 16 wherein saidwound wires include electrical insulation thereabout, and said outertubular layer and said electrical insulation about said wound wiresdefine said removed section. .Iaddend..Iadd.29. An electrode-carryingcatheter, comprising:(A) elongate, flexible tubing defining a proximalend, a distal end, and an electrically insulative outer tubular layerintermediate said ends, said tubing including a flexible non-conductivecore-covering layer about said core, said core being a stranded andtwisted configuration of annealed stainless steel wire having anappreciable torsional strength and a slow return after lateral bending,said core-covering layer being softer than said outer tubular layer andover-extruded over said core; (B) at least one electrically conductivering electrode crimped on and flush with said outer tubular layer; and(C) conducting means for conducting electrical signals between saidproximal end and each of said at least one ring electrode, saidconducting means including, intermediate said core and said outertubular layer, a longitudinally-spaced plurality of flexibleelectrically conductive wires helically wound around and at leastpartially into said core-covering layer and insulated from one anotherat least by said core-covering layer and insulated from one another atleast by said core-covering layer and from the environment at least bysaid outer tubular layer, said outer tubular layer defining a removedsection beneath a segment of each of said at least one ring electrode toenable electrical contact between a respective one of said wound wiresand a respective one of said at least one ring electrode, saidconducting means further including electrically conductive flexible flatmeans disposed intermediate each of said at least one ring electrode andsaid tubing for providing electrical communication between one said atleast one ring electrode and one of said wound wires, each of said flatmeans being a flat cooper ribbon having a pair of opposed ends, saidribbon being electrically physically joined by welding at one end to arespective one of said wound wires, wrapped under tension completelyabout said outer tubular layer, and physically joined by welding at theother end to itself, each of said at least one ring electrode beingcrimped onto a respective one of said flat means and said out tubularlayer, said at least one ring electrode crimped onto said flat means andsaid outer tubular layer being also welded to said flat means, and saidouter tubular layer being reformed about said at least one ringelectrode, said outer tubular layer being over-extruded over said woundwires and said core-covering layer; said core having an extensionprojecting distally from said distal end and an electrically conductiveend electrode being crimped distally onto said core extension andproximally crimped onto and radially flush with said outer tubularlayer. .Iaddend..Iadd.30. The catheter of claim 29 wherein said woundwires include electrical insulation thereabout, and said outer tubularlayer and said electrical insulation about said wound wires define saidremoved section. .Iaddend.